We wait until we're about a month out... pre-registration still had a few kinks in October, but I've heard its gotten better. All it really does is to streamline your request for repeater goodies and get them your departure information. They still need your CC swipe, which can take time when they're processing a bus load of folks.

Everyone should sign up for the romance reward s and you should pre-register about a week ahead of time. You can choose you minibar booze and such but you don't want to do it too early. Once you get there you can also sign up to do a trading places at the sister resort but you have to be a romance rewards member. It's a nice perk!